paraxial mesoderm splits into trunk somites and cephalic somitomeres. Trunk somites further split into sclerotome and dermatmyotome. Cephalic somiomeres split into skelatal and muscle portions of the head

BMP 4

made by migrating mesodermcauses mesoderm to form ventral mesoderm.

What does henson's node do to BMP 4?

block the action of BMP 4 and the dorsal mesdoerm is then able to form

paired condensation of mesenchyme around notocord. Each condensation consists of loosely packed cells cranially and very densely packed cells caudally

secondary sclerotome

cranial part of densely packed cells seperate and forms th annulus fibrous of innervertebalr disks. fusion of densely packed cells of cranial primary sclerotome with loosely packed cells of adjacent caudal primary sclerotome. this causes a caudal shift of one half segment in vertebral so SN can come out between

what forms from ventromedial part of somites

sclerotome

hemivertebrae

failure of primary or secondary sclerotome to develp on one side so causes only half of vertbrate and scholisos

what happens if one lacks a somite?

missing spinal nerve

what happens is lack sclerotome?

2 spinal nerves with division between them

only place skeltal muscle develops from

paraxial mesoderm

how do somites split?

into sclerotome to form axial skeleton and into dermamyotome. dermamytome splits into dermatome to form dermis and myotome to form all skeletal muscle

what forms head musculature?

forms from myotome from the seven soitomers and the four occipital somites.

vertbrate is intersegmentally between somites. due to splitting of schlerotome

what does annulus fibrosis arise from?

schlerotome

schlerotome invades somatic mesoderm to form what?

ribs

what happens if schlerotome does not meed dorsally around the notocord

spinal bifida occluta

lack of somite or schlerotome malformation

hemivertebrate

how are spinal nerves formed?

sclerotome induces spinal nerve to grow out of between the vertbrate and associate with corresponding myotome so as myotome moves, it take spinal nerve with it

In nerual epitheilum where does cell division take place?

ventricular surface

where does differentiatin occur in neural epithelium?

subpial surface

Where is neural tube epithelial cells apical surface

toward lumen. basal surface is facing surrounding mesoderm

whats unusual about neural epithelium?

cells divide at the apical surface migrate to basal surface for DNA replication then migrate back to apical surface for cell division. basically the germinally layer is the apical layer of the pseudostratisfied epithelium

Derivitives of Neuroepithelium

all cells seen in CNS
the three main derivites are bipolar neuroblast, glialblast, and ependyman cells

What are the derivities of glialblasts?

protoplasmic astrocyte, fibrillar astrocye, and oligodendrocytes

what do bipolar neuroblast form?

multipolar neuroblast

what do protoplasmic astrocytes form?

gray matter

what do fibrillar astrocytes form?

white matter

what is the phagocytic glial cell

microglia

what do oligodendrocytes form?

myelin in CNS

what purpose does apoptosisi serve?

refines number of cells

specicialized neuroepithelial cells that line neural canal

ependymal cells

what astrocytes support the neurons?

fibrilar and protoplasmic astrocytes

where fo microglia arise from?

mesenchymal cells

what secondarily invades spinal cord and brain?

vasculature. when vasculature comes in, mesenchymal cells also come in that form the microglia

defect in fusion of pleuroperitoneal membrane with septum transversum and mesoesophagus. Always occurs in dorsolateral side of diapgram usually on left side because liver is on right. Intestines get in pleua cavity and neonate usually dies because of hypoplastic lungs

innervation of diaphragm

c3,4,5 phrenic n. These nerves innervate the myatome and the myatome grows down taking the neves with it

what happens with neonate with diaphragmatic hernia

the intestine get into the thoracic cavity causing hypoplastic lungs. Neonate usually dies do to respiratory distress syndrome

by what week is the diaphragm formed?

week 7

after head fold what is heart located dorsal to ?

heart is located dorsal to pericardial cavity after head fold

what suspends heart immidiately after body folding?

mesocardium but it late degenerates

What is arterial end of heart suspended?

its suspended cranially in branchial arches

when does formation of cardiovascualr system start?

beginning of week 3

formation of primary heart tube

cardiac region forms from splanic meoderm in cranial part of embryo, lateral folding brings paired lateral endothelial tubes together to fuse and form a single heart tube. head folding brings heart ventrally and caudally

functions of bringing heard ventrally and caudally with head folding

1. septum transversum caudal to heart
2. venous end is caudal and arterial end is cranial
3.heart is dorsal to pericardial colom

heart tube elongates
bulboventricular loop formed
primitve ventricle is moved cadual and to left, primitive atrium is moved cranially, dorsally, and to right

dextrocarda

abnormal balboventricular looping where it folds to left

when mesocardium degenerates what is it and what is it's function?

Forms transverse pericardial sinus. the space seperates the arterial and venous ends of the heart

myocardium is what?

cardiac muscle

epicardium is what?

VISCERAL PERICARDIUM

what is most cranial portion of primary heart tube?

bulbous cordis and truncus arteriosus

what must ocur to place primitve chambers into anatomical locaitn?

heart must undergo looping

in formation of bulboventricular looping, how is is bulbus cordis moved?

ventrally, caudally, and to the right. All cranial structures are moved ventrally and caudally

how is the primitive ventricle moved in bulboventricualr looping?

caudally and to the left

location of pericardial colelom in reguards to the heart

it is ventralto the heart

describe normal blood throught fetal heart

oxygenated blood from placentat goes to right atrium by inferior vena cava , oxyegenated blood goes from R to L atrium throught foramen ovale. deoxygenated blood from head and neck are returned to heart via superior vena cava. deoxygenated blood goes from R atrium to R ventricle through R AV canal then out of R ventricle to pulmonary trunk but since no lungs, shunted throught ducturs arterious to aorta systemic circluation

foramen ovale

provides R to L shunt during fetal development to allow oxygenated blood to get to systemic circulation rapidly

Direct exposure of the spinal cord neural tissue to the outside because no vertebral arch or posterior body wall formed above it.

Protrusion of the meninges and the nervous tissue of the brain through a bony defect in the skull.

Meningo-encephalocele

The top of the primitive streak that includes the pit. Induces the body axis. Left-right axis is formed by cilia in this node that constantly beat in a left to right direction moving growth factors to the right.

Henson’s node

Precartilage condensation

An aggregation of mesenchymal cells that have differentiated into chondroblasts and are destined to become cartilage.

Cells that have differentiated to the extent that they are destined to be come cartilage.

Chondroblasts

Cells that secrete and maintain the cartilage matrix

Chondrocytes

site of the secondary center of ossification

epipheseal plate

Mesenchymal cells that give rise to joints

Interzonal mesenchyme

Whats intersegmental and segmental to somites?

Verbrate are intersegmental and spinal nerves are segmental

What thickens thin membrane formed by lateral plate somatic mesoderm?

somitic mesoder (hypaxial mesoderm) In the ventral body wall this thickens the thin membrane formed from the somatic, lateral-plate mesoderm. Failure for this to occur causes thoracoschisis or gastroschisis.

Homeobox genes (hox genes)

Genes for transcription factors that control the segmentation of somites. These are expressed temporally in their 3’ to 5’ order. Since development is temporally cranial to caudal the more 3’ genes are more cranial.

MyoD

A transcription factor that regulates differentiation into skeletal muscle

Factor produced by the dorsal neural tube and epidermis that induces the formation of the dermamyotome.

wnt

wHAT DO CELLS MIGRATING TO MANTLE ZONE BECOME?

NEUROBLASTS OR GLIALBLASTS

Phagocytic glia that come from blood mesenchyme not from glioblasts. They are brought along with blood vessels that invade the brain.

Microglia

An ingrowth from the somatic mesoderm (from lateral to medial) to divide the pleural and peritoneal canals. Forms the dorsolateral diaphragm.

Pleuroperitoneal membrane

WHAT Carries the phrenic nerve from the body wall to the middle mediastinum.

Pleuropericardial membrane

Aorticopulmonary septum

Septum that forms to divide the two great arteries and forms the membranous interventricular septum. Develops from neural crest cells (because great vessels come from the 6th aortic arch). This means that head & neck developmental problems are associated with membranous VSD’s.

Vasculogenesis

Formation of new blood vessels de novo. Blood islands form. Then the islands canalize. Then multiple islands connect their lumens together.

Angiogenesis

Formation of new blood vessels from other vessels.

Hemangioblast

Cell that forms the blood islands.

Hematopoeisis

Formation of blood cells. Begins in the yolk sac. Moves to the liver (and a little bit to the spleen). During the late fetal period the stem cells migrate to bone marrow to give rise to adult blood cells. Embryonic stem cells are from extraembryonic Splanchnic mesoderm. Fetal and adult are from the aortico-gonado-mesonephro regions.

Aortic arches

Transitory structures that connect the truncus arteriosus to the dorsal aortae. I-IV form part of systemic circuit. V degenerates. VI forms the pulmonary trunk.

Primitive circulation to the yolk sac. Forms the mesenteric arteries and hepatic portal venous system in the adult.

Vitelline system

What forms the Embryonic system?

The combination of the dorsal aortae and the cardinal veins that form the systemic circulation of the embryo and develop into the systemic circulation of the adult.

Open connection between the pulmonary artery and the descending aorta. Caused by premature birth, rubella in mother, or other heart defects.

Patent ductus arteriosus

Main artery in embryo gives ventral branches that become the vitellines, lateral branches that become the gonadal and renal, and dorsolateral branches that split to give the intercostals and intervertebrals.

Dorsal aorta

Go to gut tube. Initially there are very many from aorta. By adult there are celiac, sup. Mesenteric, and inf. mesenteric.

Vitelline arteries

Umbilical arteries

Take poorly oxygenated blood to the placenta. Shift origin from aorta to internal illiacs.

it grows craniallly from the floor of the inferiior buloventricular ridge but stops before it meets the endocardial cushions, this forms interventricular foramen whcih communicates between right and left ventricles

membranous portion of interventriclar septum grows from what?

forms from the aorticopulmonary septum and grows down from bulbous cordis and fuses with endocardial cusions and the muscular interventricular septum

What closes the interventricular foramen that was made by the muscular septum?

it is closed by the membranous portion of the intervventricular septum

cavitation within the ventricular walls

trabeculae carnae

what attach valve to cusps

papillary muscles and chordae tendineae

most common type of cardiac defect

VSD

What walls are thicker atrium or ventricular?

VENTRICULAR ARE THICKER AND ROUGHER

what is membranous VSD

incompleter formation of membranous interentricular septum. most common VSD

what occurs from large membranous VSD?

massive left to right shunting of blood, causes pulmonary hypertension after birth

What occurs from small membranous VSD?

usuually asympymatic

Uncommon VSD

muscular VSD

the division of the bulbus cordis and truncus arteriosus forms what two outflow tracts